The present invention generally relates to chemical sensors for monitoring, detecting and/or measuring parameters at locations remote from detection instrumentation. More particularly, the invention relates to chemical sensor components that are positioned at a remote or distal portion of an optical fiber waveguide, which chemical sensor components incorporate a polymer gel that was photocrosslinked in place and into which a dye component has been absorbed, the dye component being responsive to a parameter within a fluid being monitored.
Fiber optical chemical sensors are generally known to be useful for a wide variety of purposes, especially in the areas of medicine, scientific research, industrial applications, and the like. Descriptive materials that discuss the structure, properties, functions and operational details of fiber optic chemical sensors include U.S. Pat. No. 4,577,109 (Hirschfeld) and Sietz, "Chemical Sensors Based on Fiber Optics", Analytical Chemistry, Vol. 56, No. 1, January, 1984, each of which is incorporated by reference hereinto. From publications such as these, it is known to incorporate a chemical sensor into a fiber optic waveguide in a manner such that the chemical sensor will interact with the analyte. The chemical sensor composition and analyte interaction results in a change in optical properties, which change is probed and detected through the fiber optic waveguide. These optical properties of the chemical sensor compositions typically involve changes in colors or in color intensities. In these types of systems, it is possible to detect particularly minute changes in the parameter being monitored in order to thereby provide especially sensitive monitoring capabilities.
A specific application of this fiber optic chemical sensor technology is found in U.S. Pat. No. 4,200,110 (Peterson et al), which shows a fiber optic pH probe. This patent is incorporated by reference hereinto. Other parameters that are typically suitable for measurement by fiber optic chemical sensors include oxygen concentrations and carbon dioxide concentrations which, together with pH, are typical blood parameters that need to be monitored in vivo. Fiber optic chemical sensors can also be used to detect metal ions such as Al.sup.+++ and Be.sup.++ and other metal ions that can be determined fluorometrically when in solution, including Mg.sup.++, Zn.sup.++ and Cd.sup.++. Other uses for these types of devices include detection of biological fluids, glucose, ammonia, UO.sup.++ and halides, the detection of which may require that reagents be diffused into the sample. Other areas in which fiber optic chemical sensors may be useful include the monitoring of chemical conditions during industrial processes, such as for taking industrial biological measurements. An example of a specific industrial type of application could include the use of long-length optical fibers in order to measure conditions within submerged wells or the like.
A typical approach in the construction of fiber optic chemical sensors requires the positioning of the dye material at a generally distal location with the assistance of various different support means. The support means must be such as to permit interaction between the dye material and the substance being subjected to monitoring, measurement and/or detection. Exemplary means include permeable membranes, microencapsulation, and the use of a gel-like support. Formation of a gel-like support can include a procedure of polymerizing monomers which can be volatile and potentially toxic in the presence of a crosslinking agent. Such a procedure tends to require relatively long production time periods and appropriate monomer polymerization conditions.
It has been found that, by proceeding in accordance with the present invention, it is possible to rapidly and efficiently provide a fiber optic chemical sensor having a polymeric gel that suitably positions the dye material. Polymers are used which are of a type that can be crosslinked while within or on the distal end portion of the fiber optic waveguide, which crosslinking takes place rapidly and can be controlled to a substantial degree.
In summary, the present invention is a fiber optic chemical sensor and method for making same, which product and method utilize photocrosslinkable polymers that rapidly crosslink when subjected to actinic radiation. Such photocrosslinking is accomplished in place while the polymer is positioned at the distal end portion of a fiber optic waveguide. The dye material is thereafter absorbed into the photocrosslinked polymer in order to form a dye-containing crosslinked polymeric gel. In their pre-crosslinked condition, the gel-producing crosslinkable polymers suitable for use in accordance with this invention are soluble in a suitable solvent and typically include a vinyl-type base polymer component, especially of the vinyl aromatic type, which base polymer is preferably modified by covalent attachment of vinyl and/or acrylic groups, and same may be further modified by covalent attachment of additional chemical groups.
It is a general object of the present invention to provide an improved fiber optic chemical sensor.
Another object of the present invention is to provide an improved fiber optic chemical sensor that utilizes photoinitiated crosslinking of a polymer in order to form an expanded-volume polymer gel.
Another object of the present invention is to provide an improved fiber optic chemical sensor by a method which photocrosslinks a polymer in place within an optical fiber.
Another object of this invention is to provide an improved fiber optic chemical sensor which incorporates a dye material that fluoresces or otherwise modifies its color or color intensity in response to an analyte.
Another object of the present invention is to provide an improved fiber optic chemical sensor without requiring pretreatment of the fiber optic to adhere the polymeric support material to the fiber optic.
These and other objects, features and advantages of this invention will be clearly understood through a consideration of the following detailed description.